Push-pull amplifiers are among the most commonly used amplifiers for reducing distortion in electrical signals. Although the conventional push-pull amplifier has the advantage of simple design, it only serves to significantly reduce even-order distortion. Further, to achieve optimal reduction of even-order distortion, the components which comprise the prior art push-pull amplifier must be closely matched and carefully balanced. In come cases, this matching and balancing of components is impractical and imprecise.
In other applications, not only second-order distortion, but third-order distortion should be suppressed to accommodate the particular application in which the signal is being used. These applications include multi-channel video transmission, which requires excellent linearity to prevent channels from interfering with each other. An amplifier circuit which produces linearized signals has wide application in commercial TV transmission, CATV, interactive TV, and video telephone transmission.
Linearization of amplified signals has been studied for some time, but proposed solutions suffer from practical disadvantages. Matching and balancing components in the prior art push-pull amplifier can be expensive, time-consuming, and imprecise. In some cases which achieve highly linear signals, several adjustable circuit elements have been used to compensate for imprecise component matching, but these additional parts add to the size of the circuit and increase its cost. Furthermore, most of the prior designs do not even consider third-order distortion.
The present invention accordingly is addressed to these and other difficulties found in the prior art.